1. Field of the Invention
The present invention relates to a head suspension for supporting a slider of a disk drive incorporated in an information processor such as a personal computer, and to a method of processing such a head suspension.
2. Description of Related Art
A hard disk drive (HDD) such as a magnetic disk drive employs hard disks that are rotated at high speed. On each rotating hard disk, a slider attached to a head of a head suspension is slightly floated to write and read data to and from the hard disk through a transducer incorporated in the slider. Namely, the head with the slider is supported with the head suspension so that the slider may be slightly raised from the hard disk.
When stopping the disks, the magnetic disk drive must retract the slider from recording tracks of the hard disk. For this, there are two known methods, i.e., a contact start/stop (CSS) method and a load/unload (LUL) method.
FIGS. 11A to 11F show the CSS and LUL methods, in which FIGS. 11A and 11B are perspective views showing the CSS method, FIG. 11C is a perspective view showing the LUL method, and FIGS. 11D, 11E, and 11F are enlarged perspective views partly showing disk surfaces.
In FIGS. 11A and 11B, the CSS method moves a head 103 supported with a head suspension 101 to a CSS area 107 formed along an inner circumference of a hard disk 105 when the hard disk 105 is stopped. To avoid a slider 109 attached to the head 103 from being attracted to the surface of the stopped hard disk 105, the CSS method treats the surface of the hard disk 105 as shown in FIGS. 11D and 11E. The surface treatment of FIG. 11D corresponds to the hard disk of FIG. 11A. This surface treatment slightly roughens the entire surface of the hard disk 105 including the CSS area 107 by machining or spattering to provide the surface with irregularities. The surface treatment of FIG. 11E corresponds to the hard disk of FIG. 11B. This surface treatment slightly roughens the CSS area 107 of the hard disk 105 by laser processing or machining to provide the CSS area 107 with irregularities.
The LUL method of FIG. 11C is called a ramp load method. A ramp block 111 made of synthetic resin is arranged at a side of a hard disk 105. When the hard disk 105 is stopped, a head suspension 101 is moved to a retract position. At this time, a tab (load bar, ramp contact, or corner) formed at a front end of a head 103 is slid and guided along a slope of the ramp block 111 so that a slider 109 may be separated away from the hard disk 105.
In this way, the LUL method separates the slider 109 away from the hard disk 105 when the hard disk 105 is stopped. As a result, no friction occurs between the slider 109 and the hard disk 105, and even if the hard disk 105 turns while the disk drive is being carried, the slider 109 is free from friction.
On the other hand, the CSS method has some problems.
FIG. 12 is a graph of acoustic emission representing frictional changes and vibration caused by friction between the slider 109 and the hard disk 105 according to the CSS method. In FIG. 12, an abscissa indicates time (second) and an ordinate indicates force (gf).
According to the CSS method, the slider 109 takes off when the hard disk 105 is turned and lands when the hard disk 105 is stopped. Friction between the hard disk 105 and the slider 109 applies frictional force to the slider 109 in a rotating direction of the hard disk 105; In FIG. 12, a main waveform 112 indicates frictional changes on the slider 109, and a minor waveform 114 indicates vibration cased by friction the slider 109 and the hard disk 105 due to rattling that occurs when the hard disk 105 is started and stopped. In FIG. 12, the frictional changes are represented with acoustic emission.
As is apparent in FIG. 12, large frictional force occurs when the slider 109 takes off and lands. It is also known from FIG. 12 that, during the taking off and landing, the slider 109 flutters and hits the hard disk 105.
To increase the storage capacity of the hard disk 105, the fly height of the slider 109 must be minimized. To achieve this, the hard disk 105 must not have the irregularities mentioned above. In some cases, the height of the slider is limited to restrict a lubricant thickness. These situations, which are frequently seen these days, increase frictional force between the slider 109 and the hard disk 105.
When the hard disk 105 is stopped, a motor to drive the hard disk 105 is put in a free state. The motor in the free state may reversely turn to rotate the hard disk 105 in a reverse direction when, for example, the disk drive is carried. If this happens, frictional force occurs between the hard disk 105 and the slider 109, to displace a tongue of the head toward a carriage that holds the head suspension in the disk drive.
FIGS. 13A and 13B are models showing frictional force applied from a jig 113 to the slider 109 of the head suspension.
In FIG. 13A, the jig 113 gradually applies force to the head suspension. Then, outriggers 115 of the head suspension gradually deform to a state shown in FIG. 13B. The same will occur when the above-mentioned reverse rotation occurs to produce friction on the slider 109. Deformation of the outriggers 115 changes a set pitch angle of the slider 109 relative to the hard disk 105, to cause read/write errors. Another risk is to permanently deform a flexure 117 of the head suspension.
FIG. 14 explains a permanent deformation of the flexure 117.
If the deformation of the outriggers 115 advances to buckling, the flexure 117 will be permanently deformed to disable read/write operation.
FIG. 15 is a graph showing buckling according to frictional force applied to the slider 109 when the hard disk 105 reversely turns. In the graph, an abscissa indicates displacement (μm) and an ordinate indicates force (gf).
The graph of FIG. 15 shows that the flexure 117 starts to buckle when frictional force on the slider 109 exceeds 20 (gf). The frictional force further increases at a displacement of about 90 μm. This is because the outriggers 115 deeply deform to touch the surface of the hard disk 105.
The buckling of the flexure 117 excessively displaces the tongue of the head of the head suspension. To restrict displacement of the tongue, there is a head suspension having a limiter.
FIG. 16 is a perspective view partly showing a head suspension having such a limiter. In FIG. 16, the head suspension 101A has a head 103A having a tongue 119. The tongue 119 is provided with the T-shaped limiter 121. If the tongue 119 sways, the limiter 121 engages with a load beam 123, to thereby stabilize a slider 109A attached to the tongue 119. If the above-mentioned reverse rotation produces frictional force to displace the tongue 119, the limiter 121 will get in contact with a part 125 of a flexure 117A. The limiter 121, however, is originally to restrict vibration of the slider 109A, and therefore, is insufficient to restrict displacement of the tongue 119 caused by frictional force.
FIG. 17 is a graph showing deformation and buckling occurring on the flexure 117A of FIG. 16. Frictional force applied to the flexure 117A changes like that of FIG. 15, to deform and buckle the flexure 117A. In the middle of deformation of the flexure 117A, the T-shaped limiter 121 comes in contact with the part 125 of the flexure 117A. This corresponds to a linear part from a displacement of 80 μm in the graph of FIG. 17. The force applied to the flexure 117A, however, continuously increases. Namely, the limiter 121 provides no effect of suppressing the buckling of the flexure 117A.
To correctly write and read a hard disk with a slider in a disk drive employing the CSS method, what is important is to suppress deformation of a flexure when the hard disk is reversely turned (for example, refer to U.S. Pat. No. 5,771,136).